2012/10/17 by Jun Zhang, Shuhong Yang, Yang Liu +1 · 1 citation
Physics and Astronomy · #Dynamics (music) #Flux (metallurgy) #Ionosphere and magnetosphere dynamics #Magnetic field #Magnetic flux #Magnetic reconnection #Scientific Research and Discoveries #Solar and Space Plasma Dynamics #astro-ph.SR
paper · pdf · doi:10.1088/2041-8205/760/2/l29
13 pages, 1 table, 4 figures. Accepted for publication in ApJL
arxiv created 2012/10/17 · openalex publication_date 2012/11/08 · arxiv updated 2015/06/11 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Using the observations from the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory , we statistically investigate the emerging dimmings (EDs) of 24 isolated active regions (IARs) from 2010 June to 2011 May. All the IARs show EDs in lower-temperature lines (e.g., 171 Å) at their early emerging stages. Meanwhile, in higher temperature lines (e.g., 211 Å), the ED regions brighten continuously. There are two types of EDs: fan-shaped and halo-shaped. There are 19 fan-shaped EDs and 5 halo-shaped ones. The EDs appear to be delayed by several to more than ten hours relative to the first emergence of the IARs. The shortest delay is 3.6 hr and the longest is 19.0 hr. The EDs last from 3.3 hr to 14.2 hr, with a mean duration of 8.3 hr. Before the appearance of the EDs, the emergence rate of the magnetic flux of the IARs is between 1.2 × 10 19 Mx hr −1 to 1.4 × 10 20 Mx hr −1 . The larger the emergence rate is, the shorter the delay time is. While the dimmings appear, the magnetic flux of the IARs ranges from 8.8 × 10 19 Mx to 1.3 × 10 21 Mx. These observations imply that the reconfiguration of the coronal magnetic fields due to reconnection between the newly emerging flux and the surrounding existing fields results in a new thermal distribution which leads to a dimming for the cooler channel (171 Å) and brightening in the warmer channels.